Power semiconductor devices typically include highly doped Si substrates. Dopants out-diffuse from highly doped Si substrates due to high temperature, especially during epitaxial layer growth and high temperature oxidations/anneals. Si substrates highly doped with arsenic, phosphorous or boron, which are widely used in many types of low-voltage semiconductor transistor devices, are particularly susceptible to an out-diffusion tail which contributes significantly to RonA/FOMg (on-state resistance/Figure or Merit) loss of the device.
Hence, improved structures and manufacturing methods are needed to better limit dopant out-diffusion from highly doped Si substrates of power semiconductor devices.